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Thickness Measurement of Thin Films in Multilayer Structures

IP.com Disclosure Number: IPCOM000081153D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

DiGiacomo: AUTHOR

Abstract

The thickness of each layer in a thin-film structure is determined on the basis of the characteristic x-ray intensity of each element, the layer mass depth and the x-ray absorption through the upper layers. The multilayer structure is shown in Fig. 1.

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Thickness Measurement of Thin Films in Multilayer Structures

The thickness of each layer in a thin-film structure is determined on the basis of the characteristic x-ray intensity of each element, the layer mass depth and the x-ray absorption through the upper layers. The multilayer structure is shown in Fig. 1.

The x-ray measurement is performed by an electron microprobe; while the calculation of the thickness is accomplished by an intensity function derived from ionization curves at various voltages. Fig. 2 shows the intensity function in terms of mass thickness and accelerating voltage.

To perform the analysis, the x-ray intensity at a suitable voltage 4O KV (mg/cm/2/) from each layer of the sample and the standard is measured. The standard comprises layers of known thicknesses formed in the same sequence as in the sample, to minimize or eliminate backscattering effects. Next, the analytical expression is applied to each layer of the composite from the surface down, such that the thickness determined in the previous layer serves as the input for the next layer, and so on. Other input information are the measured x- ray intensity, the accelerating voltage, the layer number, N, and the absorption coefficients. The calculations are conveniently handled by a computer.

Applications of the method to Cu/Ni and SiO(2)/Al systems at 30 and 15 kilovolts, respectively, show that the method is accurate to within the electron microprobe capability for routine analysis. The...